U.S. patent number 9,002,238 [Application Number 13/765,791] was granted by the patent office on 2015-04-07 for rotary damper and image forming apparatus.
This patent grant is currently assigned to Konica Minolta Business Technologies, Inc.. The grantee listed for this patent is Naotoshi Kawai, Naoki Miyagawa, Takao Miyamoto, Noboru Oomoto, So Yano, Shoichi Yoshikawa. Invention is credited to Naotoshi Kawai, Naoki Miyagawa, Takao Miyamoto, Noboru Oomoto, So Yano, Shoichi Yoshikawa.
United States Patent |
9,002,238 |
Miyagawa , et al. |
April 7, 2015 |
Rotary damper and image forming apparatus
Abstract
A plurality of first viscoelastic bodies are disposed in
insertion holes of a first rotary member. A plurality of second
viscoelastic bodies are disposed in guide holes of a second rotary
member. Each of the first and the second viscoelastic bodies has an
elastic coefficient changing in accordance with aging due to use. A
guide member moves a contact member along the insertion hole and
the guide hole. The contact member applies a compressive load to
the first viscoelastic body. The aging of the second viscoelastic
body due to the compressive load applied thereto moves a position
of the first viscoelastic body where the compressive load is
received from the contact member toward a farther side from a
rotational shaft side.
Inventors: |
Miyagawa; Naoki (Toyokawa,
JP), Yoshikawa; Shoichi (Okazaki, JP),
Oomoto; Noboru (Toyokawa, JP), Kawai; Naotoshi
(Toyokawa, JP), Yano; So (Ibaraki, JP),
Miyamoto; Takao (Nagoya, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Miyagawa; Naoki
Yoshikawa; Shoichi
Oomoto; Noboru
Kawai; Naotoshi
Yano; So
Miyamoto; Takao |
Toyokawa
Okazaki
Toyokawa
Toyokawa
Ibaraki
Nagoya |
N/A
N/A
N/A
N/A
N/A
N/A |
JP
JP
JP
JP
JP
JP |
|
|
Assignee: |
Konica Minolta Business
Technologies, Inc. (Chiyoda-Ku, Tokyo, JP)
|
Family
ID: |
48982350 |
Appl.
No.: |
13/765,791 |
Filed: |
February 13, 2013 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20130216262 A1 |
Aug 22, 2013 |
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Foreign Application Priority Data
|
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|
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Feb 17, 2012 [JP] |
|
|
2012-032815 |
|
Current U.S.
Class: |
399/167 |
Current CPC
Class: |
G03G
15/757 (20130101); F16F 7/104 (20130101); F16F
15/124 (20130101); Y10T 74/2131 (20150115) |
Current International
Class: |
G03G
15/00 (20060101) |
Field of
Search: |
;399/167
;464/85,104,105,180 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1072260 |
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Sep 1954 |
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FR |
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50-138453 |
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May 1949 |
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JP |
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05-196054 |
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Aug 1993 |
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JP |
|
07-325445 |
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Dec 1995 |
|
JP |
|
08-226492 |
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Sep 1996 |
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JP |
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09-303413 |
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Nov 1997 |
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JP |
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11-95612 |
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Apr 1999 |
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JP |
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2000-098679 |
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Apr 2000 |
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JP |
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2001-099231 |
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Apr 2001 |
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JP |
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2001271845 |
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Oct 2001 |
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JP |
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2002-174932 |
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Jun 2002 |
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JP |
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2003-036007 |
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Feb 2003 |
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JP |
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2003-091208 |
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Mar 2003 |
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JP |
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2013/048703 |
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Apr 2013 |
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WO |
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Other References
Office Action (Decision to Grant Patent) issued on Apr. 16, 2014,
by the Japanese Patent Office in corresponding Japanese Patent
Application No. 2012-032815, and an English Translation of the
Office Action. (6 pages). cited by applicant.
|
Primary Examiner: Hyder; G. M.
Attorney, Agent or Firm: Buchanan Ingersoll & Rooney
PC
Claims
What is claimed as new and desired to be secured by Letters Patent
of the United States is:
1. A rotary damper comprising: a first rotator configured to rotate
about a rotational shaft; a second rotator configured to rotate
about the rotational shaft; at least one first viscoelastic body
disposed between the first rotator and the second rotator; and a
contact member disposed between the first rotator and the second
rotator, and configured to apply a compressive load in a rotation
direction about the rotational shaft to the at least one first
viscoelastic body while being in contact with the at least one
first viscoelastic body so that a torque is transmitted between the
first rotator and the second rotator, wherein a contact position of
the contact member to the at least one first viscoelastic body
moves in a radial direction of the rotational shaft.
2. The rotary damper according to claim 1, wherein the contact
position moves in a radial direction of the rotational shaft in
accordance with passage of time.
3. The rotary damper according to claim 1, wherein the contact
position moves in the radial direction of the rotational shaft in
accordance with change in a surrounding temperature.
4. The rotary damper according to claim 1, wherein the at least one
first viscoelastic body is disposed on one of the first rotator and
the second rotator, wherein the contact member is disposed on the
other one of the first rotator and the second rotator, and moves
along a movement line inclined with respect to a radial direction
of the other one of the first rotator and the second rotator, and
wherein, when a straight line between one of both ends of the
movement line on a side of the rotational shaft and the rotational
shaft is defined as a reference line, the other end of the movement
line is disposed at a position separated from the reference line in
a direction opposite from the rotation direction.
5. The rotary damper according to claim 4, further comprising an
elastic member provided to the other one of the first rotator and
the second rotator, and having a variable length along the movement
line, wherein the contact member moves farther from the rotational
shaft along the movement line in accordance with deformation of the
elastic member.
6. The rotary damper according to claim 5, wherein the elastic
member comprises a second viscoelastic body, wherein a reaction
force against a compressive load applied to the at least one first
viscoelastic body and a centrifugal force based on rotation cause
compressive deformation of the second viscoelastic body, and
wherein the contact position moves farther from the rotational
shaft along the movement line in accordance with the compressive
deformation of the second viscoelastic body.
7. The rotary damper according to claim 1, wherein, when a length
of the at least one first viscoelastic body along a rotation
direction is defined as a thickness of the at least one first
viscoelastic body, the thickness of the at least one first
viscoelastic body on a farther side from the rotational shaft is
larger than the thickness of the at least one first viscoelastic
body on a side of the rotational shaft.
8. The rotary damper according to claim 1, wherein when a length of
the at least one first viscoelastic body along the rotational shaft
is defined as a width of the at least one first viscoelastic body,
the width of the at least one first viscoelastic body on a farther
side from the rotational shaft is smaller than the width of the at
least one first viscoelastic body on a side of the rotational
shaft.
9. An image forming apparatus configured to form a toner image on a
recording medium, comprising: an image carrier configured to be
drivingly rotated; a developing unit comprising a developing roller
forming the toner image on the image carrier; and the rotary damper
according to claim 1 disposed on a rotational shaft of the image
carrier or the developing roller.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. .sctn.119
to Japanese Patent Application No. 2012-032815, filed Feb. 17,
2012. The contents of this application are incorporated herein by
reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotary damper and an image
forming apparatus.
2. Discussion of the Background
A technique has been conventionally known in which an
anti-vibration rubber is provided between gears in a driving device
that drivingly rotates a photoreceptor drum used in an
electrophotographic copier to prevent transmission of vibration to
the photoreceptor drum (see, for example, Japanese Unexamined
Patent Application Publication No. 2002-174932).
A technique has also been known in which a flow rate of a viscous
fluid is changed to keep a rotational vibration damping constant
the same between low and high revolution times (see for example,
Japanese Unexamined Patent Application Publication No.
2001-099231).
In an image forming apparatus of the Japanese Unexamined Patent
Application Publication No. 2002-174932, the vibration is absorbed
by the elastic deformation of the anti-vibration rubber and thus is
prevented from being transmitted to the photoreceptor drum.
However, if the elastic coefficient of the anti-vibration rubber
changes over time in accordance with a used period, or in
accordance with a change in the surrounding temperature, the
deformation amount value of the anti-vibration rubber changes in
accordance with the used period or the surrounding temperature.
Thus, the vibration damping effect cannot be stably obtained. As a
result, the transmission of the vibration to the photoreceptor drum
cannot be favorably prevented, and periodical unevenness occurs in
images to be transferred onto a recording medium.
Thus, an object of the present invention is to provide a rotary
damper that can efficiently prevent the transmission of the
vibration regardless of the used environment
SUMMARY OF THE INVENTION
To achieve the object, a first aspect of the present invention is a
rotary damper including: a first rotator configured to rotate about
a rotational shaft; a second rotator configured to rotate about the
rotational shaft; at least one first viscoelastic body disposed
between the first rotator and the second rotator; and a contact
member disposed between the first rotator and the second rotator,
and configured to apply a compressive load in a rotation direction
about the rotational shaft to the first viscoelastic body while
being in contact with the first viscoelastic body so that a torque
is transmitted between the first rotator and the second rotator. A
contact position of the contact member to the first viscoelastic
body is movable.
A second aspect of the present invention is that, in the rotary
damper of the first aspect, the contact position may move in a
radial direction of the rotational shaft in accordance with passage
of time.
A third aspect of the present invention is that, in the rotary
damper of the first aspect, the contact position may move in the
radial direction of the rotational shaft in accordance with change
in a surrounding temperature.
A fourth aspect of the present invention is that, in the rotary
damper of the first aspect, the first viscoelastic body may be
disposed on one of the first rotator and the second rotator. The
contact member may be disposed on the other one of the first
rotator and the second rotator, and move along a movement line
inclined with respect to a radial direction of the other one of the
first rotator and the second rotator. When a straight line between
one of both ends of the movement line on a side of the rotational
shaft and the rotational shaft is defined as a reference line, the
other end of the movement line may be disposed at a position
separated from the reference line in a direction opposite from the
rotation direction.
A fifth aspect of the present invention is that, the rotary damper
of the fourth aspect may further include an elastic member provided
to the other one of the first rotator and the second rotator, and
having a variable length along the movement line. The contact
member may move farther from the rotational shaft along the
movement line in accordance with deformation of the elastic
member.
A sixth aspect of the present invention is that, in the rotary
damper of the fifth aspect, the elastic member may include a second
viscoelastic body. A reaction force against a compressive load
applied to the first viscoelastic body and a centrifugal force
based on rotation may cause compressive deformation of the second
viscoelastic body. The contact position may move farther from the
rotational shaft along the movement line in accordance with the
compressive deformation of the second viscoelastic body.
A seventh aspect of the present invention is that, in the rotary
damper of the first aspect, when a length of the first viscoelastic
body along a rotation direction is defined as a thickness of the
first viscoelastic body, the thickness of the first viscoelastic
body on a farther side from the rotational shaft may be larger than
the thickness of the first viscoelastic body on a side of the
rotational shaft.
A eighth aspect of the present invention is that, in the rotary
damper of the first aspect, when a length of the first viscoelastic
body along the rotational shaft is defined as a width of the first
viscoelastic body, the width of the first viscoelastic body on a
farther side from the rotational shaft may be smaller than the
width of the first viscoelastic body on a side of the rotational
shaft.
A ninth aspect of the present invention is an image forming
apparatus configured to form a toner image on a recording medium,
including: an image carrier configured to be drivingly rotated; a
developing unit including a developing roller forming the toner
image on the image carrier; and the rotary damper according to the
first aspect disposed on a rotational shaft of the image carrier or
the developing roller.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the invention and many of the
attendant advantages thereof will be readily obtained as the same
becomes better understood by reference to the following detailed
description when considered in connection with the accompanying
drawings, wherein:
FIG. 1 is a front view showing an example of an overall
configuration of an image forming apparatus of first to fourth
embodiments of the present invention;
FIG. 2 is a skeleton diagram showing a power transmission system in
a drive unit in the first to the fourth embodiments of the present
invention;
FIG. 3 is a front perspective view showing an example of a
configuration of a rotary damper of the first embodiment;
FIG. 4 is a rear perspective view showing the example of the
configuration of the rotary damper of the first embodiment;
FIG. 5 is a front perspective view showing examples of
configurations of a first viscoelastic body, a contact member, and
a second viscoelastic body of the first embodiment;
FIG. 6 is a front perspective view showing an example of a
configuration of a guide member of the first embodiment;
FIG. 7 is a front perspective view describing an example of a shape
of the first viscoelastic body of the first embodiment;
FIG. 8 is a graph showing an example of a relationship between a
spring constant at a load position and a thickness at the load
position in the first viscoelastic body of the first
embodiment;
FIG. 9 is a front view describing a load received by the second
viscoelastic body;
FIG. 10 is a front perspective view describing a position of the
contact member in an initial state before aging of the first and
the second viscoelastic bodies due to use;
FIG. 11 is a rear perspective view describing the position of the
contact member in the initial state of the first and the second
viscoelastic bodies;
FIG. 12 is a front perspective view describing a position of the
contact member when the first and the second viscoelastic bodies
undergo the aging due to use;
FIG. 13 is a rear perspective view describing the position of the
contact member when the first and the second viscoelastic bodies
undergo the aging due to use;
FIG. 14 is a front perspective view showing an example of a
configuration of a rotary damper of the second embodiment;
FIG. 15 is a front perspective view showing examples of
configurations of a first viscoelastic body, a contact member, and
a second viscoelastic body of the second embodiment;
FIG. 16 is a front perspective view describing an example of a
shape of the first viscoelastic body of the second embodiment;
FIG. 17 is a graph showing an example of a relationship between a
spring constant at a load position and a width at the load position
in the first viscoelastic body of the second embodiment;
FIG. 18 is a graph showing an example of a relationship between an
elastic coefficient of each of the first and the second
viscoelastic bodies and a temperature in a third embodiment;
FIG. 19 is a front perspective view showing an example of a
configuration of a rotary damper of the fourth embodiment; and
FIG. 20 is a rear perspective view showing the example of the
configuration of the rotary damper of the fourth embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The embodiments will now be described with reference to the
accompanying drawings, wherein like reference numerals designate
corresponding or identical elements throughout the various
drawings.
1. First Embodiment
1.1 Configuration of Image Forming Apparatus
FIG. 1 is a front view showing an example of an overall
configuration of an image forming apparatus 1 of a first embodiment
of the present invention. The image forming apparatus 1 prints a
monochrome image or a color image by electrophotography. The image
forming apparatus 1 may integrally incorporate copy, printing, fax
capabilities, and the like functions. As shown in FIG. 1, the image
forming apparatus 1 mainly includes a printer unit 10, a sheet
feeder 30, a fixing unit 40, a discharge unit 50, a scanner 55, a
display unit 80, and a controller 90.
FIG. 1 and drawings thereafter are provided with an XYZ orthogonal
coordinate system in which a Z axis direction is a vertical
direction and an XY plane is a horizontal surface, to clarify the
directional relationship in the drawings.
The printer unit 10 prints a monochrome or color image on a
recording medium P supplied through a sheet feed path R1 and a
conveyance path Ra. As shown in FIG. 1, the printer unit 10 mainly
includes image forming units 11 (11Y, 11M, 11C, and 11K), exposure
scanners 20 (20Y, 20M, 20C, and 20K), and an intermediate transfer
belt 21.
The plurality of (4 in this embodiment) image forming units 11
respectively correspond to colors of yellow (Y), magenta (M), cyan
(C), and black (K). As shown in FIG. 1, the image forming units 11
(11Y, 11M, 11C, and 11K) respectively mainly include photoreceptor
drums 13 (13Y, 13M, 13C, and 13K), chargers 14 (14Y, 14M, 14C, and
14K), developing units 16 (16Y, 16M, 16C, and 16K), primary
transfer rollers 18 (18Y, 18M, 18C, and 18K), drum cleaners 19
(19Y, 19M, 19C, and 19K), and the exposure scanners 20 (20Y, 20M,
20C, and 20K).
The printer unit 10 of this embodiment is so-called a tandem
printer, and below and along the intermediate transfer belt 21, the
image forming units 11 (11Y, 11M, 11C, and 11K) are arranged in the
order of yellow (Y), magenta (M), cyan (C), and black (K) from the
left side to the right side of FIG. 1.
In this embodiment, the image forming units 11Y, 11M, 11C, and 11K
have the same hardware configuration. Thus, the image forming unit
11Y, and the photoreceptor drum 13Y, the charger 14Y, the
developing unit 16Y, the primary transfer roller 18Y, the drum
cleaner 19Y, and the exposure scanner 20Y as the components of the
image forming unit 11Y are described in detail below.
For the convenience of illustration, the reference numerals of the
photoreceptor drums 13M, 13C, and 13K, the chargers 14M, 14C, and
14K, the developing units 16M, 16C, and 16K, the primary transfer
rollers 18M, 18C, and 18K, the drum cleaners 19M, 19C, and 19K, and
the exposure scanners 20M, 20C, and 20K are omitted in FIG. 1 and
the drawings thereafter.
The photoreceptor drum 13Y has a cylinder or column shape, and
faces the primary transfer roller 18Y with the intermediate
transfer belt 21 interposed therebetween. The photoreceptor drum
13Y includes a photoconductive film on an outer peripheral
surface.
The outer peripheral surface of the photoreceptor drum 13Y is
irradiated with light from the corresponding exposure scanner 20Y
so that charges in the irradiated area are removed. Thus, a yellow
(Y) electrostatic latent image is formed on the outer peripheral
surface of the photoreceptor drum 13Y. Similarly, magenta, cyan,
and black electrostatic latent images are respectively formed on
the outer peripheral surfaces of the photoreceptor drums 13M, 13C,
and 13K.
The charger 14Y comes into contact with the outer peripheral
surface of the photoreceptor drum 13Y to charge the outer
peripheral surface of the photoreceptor drum 13Y. The developing
unit 16Y supplies yellow (Y) toner to the photoreceptor drum 13Y on
which the electrostatic latent image is formed to form a toner
image based on the electrostatic latent image on the outer
peripheral surface of the photoreceptor drum 13Y.
As shown in FIG. 1, the primary transfer roller 18Y faces the
photoreceptor drum 13Y with the intermediate transfer belt 21
interposed therebetween. The primary transfer roller 18Y is charged
with a polarity that is opposite to that of the outer peripheral
surface of the photoreceptor drum 13Y. Thus, when the intermediate
transfer belt 21 is nipped by the rolling photoreceptor drum 13Y
and the rolling primary transfer roller 18Y, the yellow (Y) toner
image is transferred onto the intermediate transfer belt 21.
The drum cleaner 19Y removes remaining toner on the outer
peripheral surface of the photoreceptor drum 13Y after the toner
image is transferred on the intermediate transfer belt 21 and until
the next yellow toner is supplied from the developing unit 16Y. As
shown in FIG. 1, the drum cleaner 19Y is positioned to be capable
of contacting the outer peripheral surface of the photoreceptor
drum 13Y.
The exposure scanners 20 (20Y, 20M, 20C, and 20K) are so-called
exposure units that respectively irradiate the photoreceptor drums
13 (13Y, 13M, 13C, and 13K) with a laser beam. Thus, the
electrostatic latent images are formed on the outer peripheral
surfaces of the photoreceptor drums 13 (13Y, 13M, 13C, and
13K).
The intermediate transfer belt 21 transfers the toner images of the
four colors primary transferred by the image forming units 11 (11Y,
11M, 11C, and 11K), onto the recording medium P. As shown in FIG.
1, the intermediate transfer belt 21 is wound across a driving
roller 22 and a driven roller 23 that rotate in the
counterclockwise direction of FIG. 1. A secondary transfer roller
25 faces the driving roller 22 with the conveyance path Ra
interposed therebetween and contacts the outer periphery of the
intermediate transfer belt 21.
Thus, by adjusting the feed timing of the intermediate transfer
belt 21 and the conveyance timing of the recording medium P
conveyed along the conveyance path Ra, the toner image of the four
colors formed on the outer periphery of the intermediate transfer
belt 21 is secondary transferred onto the recording medium P.
A developer supplied from the developing unit 16 of the image
forming unit 11 can be a developer of one-component system using no
carrier, but may be a developer of two-component system including
toner and carrier. The material of the intermediate transfer belt
21 can be polycarbonate, polyimide, polyamidimide, and the
like.
A temperature-humidity sensor 29 is a detector that detects a
temperature and/or humidity around the printer unit 10. The voltage
to be applied to the primary transfer rollers 18 (18Y, 18M, 18C,
and 18K) and the secondary transfer roller 25 is adjusted based on
the temperature and the humidity detected by the
temperature-humidity sensor 29.
The primary and secondary transfer rollers 18 and 25 are so-called
elastic rollers that are formed by adding ion conductive materials
to synthetic rubber such as nitrile rubber and foaming the
resultant object, for example.
The sheet feeder 30 feeds the recording medium P to the printer
unit 10. As shown in FIG. 1, the sheet feeder 30 mainly includes a
sheet feed cassette 31 and a sheet feed roller 32.
The sheet feed cassette 31 is a container that can accommodate a
plurality of recording media P. The sheet feed roller 32 picks up
the recording media P accommodated in the sheet feed cassette 31
from the uppermost sheet, and supplies the picked-up recording
medium P to the sheet feed path R1.
A pair of resist rollers 33 control the timing at which the
recording medium P is fed to the conveyance path Ra. If the
"direction of conveying the recording medium P" is defined as the
"conveyance direction", the pair of resist rollers 33 are disposed
more on the downstream side than the sheet feed roller 32 in the
conveyance direction as shown in FIG. 1.
A sheet detection sensor 35 is a detector that detects the forward
end of the recording medium P. As shown in FIG. 1 the sheet
detection sensor 35 is disposed more on the downstream side than
the resist rollers 33 in the conveyance direction. When the forward
end of the recording medium P reaches the sheet detection sensor
35, the output from the sheet detection sensor 35 transitions, for
example, to an ON state from an OFF state. Thus, by monitoring the
output value outputted from the sheet detection sensor 35, whether
the recording medium P is supplied to a portion right before the
resist rollers 33 can be determined.
The fixing unit 40 fixes the toner images transferred on the
recording medium P. As shown in FIG. 1 the fixing unit 40 is
disposed more on the downstream side than the secondary transfer
roller 25 in the conveyance path Ra.
The discharge unit 50 is disposed more on the downstream side than
the fixing unit 40 in the conveyance direction, and discharges the
recording medium P on which the toner image is fixed to the outside
of the apparatus. Specifically, the recording medium P supplied to
the discharge unit 50 through the conveyance path Ra is guided to a
discharge path R2. As shown in FIG. 1, the discharge unit 50 mainly
includes a pair of discharge rollers 51 disposed on the discharge
path R2 and a discharge tray 52.
The scanner 55 is of an automatic document feeder (ADF) type or a
flat bed type and reads an image on a document. As shown in FIG. 1,
the scanner 55 is disposed above the discharge unit 50.
The display unit 80 is formed of a liquid crystal display for
example, and has a "touch panel" function of allowing a position in
a screen to be pointed by touching the screen with a finger or a
dedicated pen. Accordingly, the user of the image forming apparatus
1 (hereinafter, simply referred as "user") gives instructions by
using the "touch panel" function of the display unit 80 based on
the content displayed on the display unit 80 and thus can make the
image forming apparatus 1 execute certain processing (such as
processing of printing the toner image on the recording medium P
supplied from the sheet feeder 30). As described above, the display
unit 80 can be used as a reception unit that receives an input
operation from the user.
An operation unit 85 is an input unit including a plurality of key
pads. For example, when a print start button 86 in the operation
unit 85 is pressed, the printing processing on the recording medium
P is executed. Thus, like the display unit 80, the operation unit
85 can be used as the reception unit that receives the input
operation from the user.
As shown in FIG. 1, the controller 90 is disposed below the
discharge tray 52. The controller 90 controls the components of the
image forming apparatus 1 and executes data calculation. As shown
in FIG. 1, the controller 90 mainly includes a read only memory
(ROM) 91, a random access memory (RAM) 92, an image memory 93, and
a central processing unit (CPU) 95.
The ROM 91 is a so-called non-volatile storage unit, and stores a
program 91a for example. A flash memory that is a readable and
writable non-volatile memory may be used as the ROM 91.
The RAM 92 and the image memory 93 are each a volatile storage
unit. The RAM 92 stores data used for the calculation of the CPU 95
for example. The image memory 93 stores image data pieces
respectively corresponding to the colors of yellow (Y), magenta
(M), cyan (C), and black (K).
The CPU 95 executes a control, various data calculations, and the
like in accordance with the program 91a in the ROM 91. For example,
the CPU 95 receives an image signal from an unillustrated external
terminal and the like, converts the image signal into digitalized
image data for Y-K color, and controls the operations of the
printer unit 10, the sheet feeder 30, and the like. Thus, the
printing processing on the recording medium P is executed.
1.2 Configuration of Drive Unit
FIG. 2 is a skeleton diagram showing a power transmission system in
a drive unit 60. The drive unit 60 provides torque to the
photoreceptor drums 13 (13Y, 13M, 13C, and 13K) and the developing
units 16 (16Y, 16M, 16C, and 16K) (more specifically, the
developing rollers 17 (17Y, 17M, 17C, and 17K) and the like of the
developing units 16) of the image forming units 11 (11Y, 11M, 11C,
and 11K). As shown in FIG. 2, the drive unit 60 mainly includes a
motor 61 and a plurality of driving gears 62, 63, 65, 66, 68, and
69.
For the convenience of the illustration, FIG. 2 includes only the
photoreceptor drums 13M and 13Y among the plurality of
photoreceptor drums 13 (13Y, 13M, 13C, and 13K), the developing
unit 16Y among the plurality of the developing units 16 (16Y, 16M,
16C, and 16K), the developing roller 17 Y among the plurality of
developing rollers 17 (17Y, 17M, 17C, and 17K), rotary dampers 70Y
and 70M among a plurality of rotary dampers 70 (70Y, 70M, 70C, and
70K).
Also, in the description given below, the image forming units 11Y
to 11K, the photoreceptor drums 13Y to 13K, the developing units
16Y to 16K, the developing rollers 17Y to 17K, and the rotary
dampers 70Y to 70K are collectively referred respectively to as the
image forming unit 11, the photoreceptor drum 13, the developing
unit 16, the developing roller 17, and the rotary damper 70.
As shown in FIG. 2, the driving gear 62 is attached to the shaft
center of the motor 61, and an input side of the first relay gear
63 meshes with the driving gear 62. An output side of the first
relay gear 63 meshes with input gears 65 (65Y and 65M).
As shown in FIG. 2, the input gear 65Y, the output gear 66Y, and
the rotary damper 70Y are attached to the rotational shaft 70a of
the photoreceptor drum 13Y. The docking gear 69 is attached to the
shaft center of the developing roller 17Y of the developing unit
16Y. The second relay gear 68 has an input and output sides
respectively meshing with the output gear 66Y and the docking gear
69.
Thus, the photoreceptor drum 13Y is rotated by the torque
transmitted from the rotary damper 70Y. The developing roller 17Y
is rotated by the torque transmitted through the rotary damper 70Y,
the second relay gear 68, and the docking gear 69. Specifically,
the torque of the motor 61 is branched at a photoreceptor driving
system (for example, the output gear 66Y provided to the rotational
shaft 70a of the photoreceptor drum 13Y). The branched torque is
transmitted to the developing roller 17Y.
Similarly, as shown in FIG. 2, the input gear 65M, the output gear
66M, the rotary damper 70M are attached to the rotational shaft 70a
of the photoreceptor drum 13M. Thus, the rotary damper 70M is
rotated by the torque transmitted through the driving gear 62, the
first relay gear 63, the input gear 65, and the rotary damper
70.
1.3 Configuration of Rotary Damper
FIG. 3 and FIG. 4 are respectively front and rear perspective views
showing an example of a configuration of the rotary damper 70 of
this embodiment. FIG. 5 is a front perspective view showing
examples of configurations of first and second viscoelastic bodies
73 and 74 and contact members 77 of this embodiment. FIG. 6 is a
front perspective view showing an example of a configuration of a
guide member 76 of this embodiment.
The rotary damper 70 transmits the driving force from the motor 61
(driving source) to the photoreceptor drum 13. As shown in FIG. 3
to FIG. 6, the rotary damper 70 mainly includes a first rotary
member 71, a second rotary member 72, the first and the second
viscoelastic bodies 73 and 74, guide members 76, and the contact
members 77.
The first rotary member 71 is a rotator on a driven body side and
is provided closer to the photoreceptor drum 13 side than the
second rotary member 72 on the rotational shaft 70a. As shown in
FIG. 3, the first rotary member 71 is a disk shaped plate that
rotates about the rotating shaft 70a in the direction indicated by
an arrow AR1 (hereinafter, also simply referred to as "rotation
direction"). A plurality of (four in this embodiment) insertion
holes 71a are long through-holes formed on the first rotary member
71. As shown in FIG. 3, the insertion holes 71a extend in a radial
pattern from the shaft center side of the rotational shaft 70a
(hereinafter, also simply referred to as "rotational shaft 70a
side"), to the farther side in the radial direction from the
rotational shaft 70a (hereinafter, also simply referred to as
"farther side").
The second rotary member 72 is a rotator on a driving body side and
is provided closer to the motor 61 side than the first rotary
member 71 on the rotational shaft 70a. As shown in FIG. 4, the
second rotary member 72 is a disk shaped plate that rotates about
the rotational shaft 70a in the rotation direction. The second
rotary member 72 is disposed concentrically with respect to the
first rotary member 71. A plurality of (four in this embodiment)
guide holes 72a are long through-holes formed on the second rotary
member 72. The guide holes 72a extend radially toward the farther
side from the rotational shaft 70a side as shown in FIG. 4.
In this embodiment, it is described that the first and the second
rotary members 71 and 72 are rotators respectively on the driven
and driving sides. Alternatively, the first and the second rotary
members 71 and 72 may be rotators respectively on the driving and
driven sides.
In this embodiment, the first and the second rotary members 71 and
72 rotate about the rotational shaft 70a, but this should not be
construed as a limiting sense. For example, the rotational shafts
of the first and second rotary members 71 and 72 may be separate
members having substantially the same longitudinal shaft
center.
As the rotation of the rotational shaft 70a rotates the second
rotary member 72, the torque is provided to the contact member 77
through the guide member 76 on the second rotary member 72. Thus,
the compressive load is applied to the first viscoelastic body 73
on the first rotary member 71, whereby the first rotary member 71
rotates. A vibration damping effect is obtained by thus
transmitting the running torque.
As shown in FIG. 3 and FIG. 4, the first and the second
viscoelastic bodies 73 and 74 are disposed between the first and
the second rotary members 71 and 72. For example, a plurality of
(four in this embodiment) the first viscoelastic bodies 73 are
disposed in the insertion holes 71a of the first rotary member 71.
A plurality of (four in this embodiment) the second viscoelastic
bodies 74 are disposed in guide holes 72a of the second rotary
member 72.
Viscoelastic bodies of which an elastic coefficient changes
("decreases" in this embodiment) by aging due to use are used as
the first and the second viscoelastic bodies 73 and 74 of this
embodiment. Specifically, the first and the second viscoelastic
bodies 73 and 74 may be made of an anti-vibration rubber such as
NonBuren S15 and NonBuren S30 manufactured by Hirakata Giken,
Inc.
The guide member 76 is disposed on the second rotary member 72, and
allows the contact member 77 to move along the insertion hole 71a
and the guide hole 72a. As shown in FIG. 6, the guide member 76
mainly includes a block 76a and a bar 76b.
The guide member 76 is disposed in such a manner as to communicate
the first and the second rotary members 71 and 72 with one another.
The guide member 76 transmits the torque from the second rotary
member 72 to the first viscoelastic body 73, and can be regarded as
a component of the second rotary member 72.
The block 76a is a sliding member that slides along a center line
(hereinafter, also simply referred to as "movement line") 76c of
the guide hole 72a in the direction indicated by an arrow AR2
(hereinafter, also simply referred to as "radial direction"). The
width of the block 76a in the rotation direction may be set to be
not larger than the width of the guide hole 72a.
The side wall of the block 76a and the inner wall of the second
rotary member 72 constituting the guide hole 72a may be
respectively provided with a protrusion and a recess to be engaged,
so that the block 76a can move along the guide hole 72a. The guide
member 76 may be removable from the guide hole 72a for maintenance
and the like.
As shown in FIG. 4, the block 76a, and the second viscoelastic body
74 are inserted in the guide hole 72a while respectively being
disposed on the rotating shaft 70a side and on the farther side.
Thus, when the second rotary member 72 rotates in the rotation
direction, the resultant centrifugal force brings the block 76a
into contact with the second viscoelastic body 74, and the block
76a applies the compressive load to the second viscoelastic body
74.
The bar 76b is a shaft center fixed on the block 76a. As shown in
FIG. 3 to FIG. 6, while the block 76a is inserted in the guide hole
72a, extending directions of the bar 76b and the rotational shaft
70a are parallel with each other.
The contact member 77 is a cylindrical body that rotates with the
bar 76b serving as the shaft center. As shown in FIG. 3 and FIG. 5,
the contact member 77 is disposed between the first and the second
rotary members 71 and 72, like the first and the second
viscoelastic bodies 73 and 74. The bar 76b is inserted in the
hollow portion in the center of the contact member 77. The contact
member 77 is rotatable with respect to the bar 76b.
1.4 Shape of First Viscoelastic Body
FIG. 7 is a front perspective view describing an example of a shape
of the first viscoelastic body 73 of this embodiment. As shown in
FIG. 7, the first viscoelastic body 73 has a trapezoidal shape as
viewed in a direction parallel with the rotational shaft 70a.
In this embodiment, lengths of the first viscoelastic body 73 along
the rotation direction and the rotational shaft 70a are defined
respectively as a thickness Th and a width W. Here, a thickness Th1
of the first viscoelastic body 73 on the farther side (for example,
load position LP1) is set to be larger than a thickness Th2 of the
first viscoelastic body 73 on the rotational shaft 70a side (for
example, load position LP2) as shown in FIG. 7.
Specifically, as shown in FIG. 7, the first viscoelastic body 73
has the uniform width W from the rotational shaft 70a side to the
farther side, and has the thickness Th gradually increasing toward
the farther side from the rotational shaft 70a side.
A spring constant K of the first viscoelastic body 73 at each of
the load positions LP1 and LP2 can be regarded as being equal to
that obtained by arranging a plurality of spring bodies having the
same width W in series. Thus, assuming that the first viscoelastic
body 73 at each of the load positions LP1 and LP2 includes two
spring bodies (respectively having spring constants k1 and k2), the
spring constant K of the first viscoelastic body 73 at each of the
load positions LP1 and LP2 can be expressed as in the following
formula (1). 1/K=1/k1+1/k2 (1)
FIG. 8 is a graph showing a relationship between the spring
constant K of the first viscoelastic body 73 at a position to which
the load is applied and a thickness Th of the first viscoelastic
body 73 at the position. In FIG. 8, the horizontal axis represents
the thickness Th (mm) of the first viscoelastic body 73, and the
vertical axis represents the spring constant K (N/m) of the first
viscoelastic body 73 corresponding to the thickness Th. Leader
lines of the reference numerals LP1 and LP2 in FIG. 8 indicate
respectively the thicknesses Th and the spring constants K at the
load positions LP1 and LP2 of the first viscoelastic body 173.
As can be understood from the formula (1) and FIG. 8, the spring
constant K of the first viscoelastic body 73 at each of the load
positions LP1 and LP2 decreases as the thickness Th of the first
viscoelastic body 73 increases.
Thus, the spring constant K of the first viscoelastic body 73 on
the farther side is smaller than the spring constant K of the first
viscoelastic body 73 on the rotational shaft 70a side. If a
constant torque is transmitted between the first and the second
rotary members 71 and 72, the compressive load applied to the first
viscoelastic body 73 from the contact member 77 gradually decreases
toward the farther side from the rotational shaft 70a side.
Thus, even when the contact member 77 moves toward the farther side
of the rotational shaft 70a in accordance with the aging of the
second viscoelastic body 74 due to use, the torsion angles of the
first and the second rotary members 71 and 72 are kept within a
predetermined range.
1.5 Operation of Rotary Damper
FIG. 9 is a front view describing a load received by the second
viscoelastic body 74. FIG. 10 and FIG. 11 are respectively front
and rear perspective views describing a position of the contact
member 77 in an initial state, that is, a state before the aging
due to use, of the first and the second viscoelastic bodies 73 and
74. FIG. 12 and FIG. 13 are respectively front and rear perspective
views describing a position of the contact member 77 when the first
and the second viscoelastic bodies 73 and 74 undergo the aging due
to use.
Here, the force applied to the second viscoelastic body 74 while
the first and the second rotary members 71 and 72 are rotating is
described, and then the operation of the rotary damper 70 when the
first and the second viscoelastic bodies 73 and 74 undergo the
aging due to use is described.
As shown in FIG. 9, when a compressive load F1 is applied to the
first viscoelastic body 73 from the contact member 77, the contact
member 77 receives a reaction force F2 as the reaction against the
compressive load F1. Furthermore, the contact member 77 receives a
centrifugal force F3 based on the rotation. Thus, the block 76a of
the guide member 76 receives a resultant force FR of the reaction
force F2 and the centrifugal force F3. Thus, the block 76a of the
guide member 76 transmits the resultant force FR to the second
viscoelastic body 74 along the guide hole 72a. Therefore, the
reaction force F2 against the compressive load applied to the first
viscoelastic body 73 and the centrifugal force F3 based on the
rotation cause the compressive deformation of the second
viscoelastic body 74.
When a straight line 76d between one end E1, on the rotational
shaft 70a side, of the movement line 76c and the rotational shaft
70a is defined as "reference line", the other end E2 of the
movement line 76c is disposed at a position separated from the
reference line 76d in a direction opposite from that indicated by
the arrow AR1.
As shown in FIG. 5, a long hole space formed by the insertion hole
71a includes a portion occupied by the first viscoelastic body 73
and a remaining portion. The remaining portion is used as a guide
groove guiding the contact member 77 in a radial direction of the
first rotary member 71. The contact member 77 moves along the guide
groove while being in contact with the first viscoelastic body 73
in accordance with the resultant force FR and the aging of the
second viscoelastic body 74.
Thus, the contact member 77 moves from the rotational shaft 70a
side towards the farther side along the insertion hole 71a.
Specifically, as shown in FIG. 4, the contact member 77 moves along
the movement line 76c inclined with respect to the radial direction
of the second rotary member 72. Accordingly, the first viscoelastic
body 73 transmits the torque at a position free of aging due to
use, and thus a predetermined vibration damping effect can be
stably obtained.
As described above, among the components of the rotary damper 70,
the first and the second viscoelastic bodies 73 and 74, the guide
member 76, and the contact member 77 are particularly used as a
drive transmission system transmitting the torque between the first
and the second rotary members 71 and 72.
In other words, the first and the second viscoelastic bodies 73 and
74, the guide member 76, and the contact member 77 constitute a
movement mechanism that makes the position at which the compressive
load is applied to the first viscoelastic body 73 movable in
accordance with the change in the used environment such as elapse
of running time.
1.6 Advantage of Rotary Damper of First Embodiment
As described above, in the rotary damper 70 of the first
embodiment, the contact member 77 moves toward the farther side
from the rotational shaft 70a side along the first viscoelastic
body 73 in accordance with the aging of the first viscoelastic body
73. Thus, the first viscoelastic body 73 can transmit the torque at
a position free of aging due to use. Accordingly, the aging of the
second viscoelastic body 74 due to the compressive load applied
thereto moves the position where the first viscoelastic body 73
receives the compressive load from the contact member 77 toward the
farther side from the rotational shaft 70a side. Thus, a
predetermined vibration damping effect can be stably obtained.
When the torque is transmitted between the first and the second
rotary members 71 and 72, the resultant force FR of the reaction
force F2 produced by being in contact with the first viscoelastic
body 73 and the centrifugal force F3 produced by the rotation
causes the compressive deformation of the second viscoelastic body
74.
The aging due to use gradually shortens the length of the second
viscoelastic body 74 along the movement line 76c, and gradually
moves the position where the first viscoelastic body 73 receives
the compressive load from the contact member 77 toward the farther
side from the rotational shaft 70a side along the first
viscoelastic body 73 (radial direction).
Accordingly, by associating the aging of the first viscoelastic
body 73 and the aging of the second viscoelastic body 74, the first
viscoelastic body 73 can transmit the torque at a position free of
the aging due to use. Therefore, a predetermined vibration damping
effect can be stably obtained even when the first viscoelastic body
73 has a uniform thickness Th and a uniform width W in the radial
direction.
When the width W of the first viscoelastic body 73 on the farther
side is set to be larger than the width W of the first viscoelastic
body 73 on the rotational shaft 70a side, the first viscoelastic
body 73 has a smaller spring constant on the farther side than on
the rotational shaft 70a side.
If the constant torque is transmitted between the first and the
second rotary members 71 and 72, the compressive load received by
the first viscoelastic body 73 from the contact member 77 decreases
toward the farther side from the rotational shaft 70a side.
Thus, even when the contact member 77 moves from the rotational
shaft 70a side to the farther side, the torsion angles of the first
and the second rotary members 71 and 72 can be kept within a
predetermined range. Thus, even more stable vibration damping
effect can be obtained.
Moreover, the contact member 77 that rotates with the bar 76b
serving as the shaft center is in contact with the first
viscoelastic body 73. Thus, the driving force in the rotation
direction serves as the load received by the first viscoelastic
body 73. Accordingly, influence of wear and friction on the contact
surface can be reduced. Therefore, even more stable vibration
damping effect can be obtained.
2. Second Embodiment
Next, a second embodiment of the present invention will be
described. The rotary damper 70 of the first embodiment and a
rotary damper 170 of the second embodiment have the same
configuration except that the first viscoelastic body 73 and its
counterpart, a first viscoelastic body 173, have different
configurations. Thus, the difference is mainly described below.
Components common in the rotary dampers 70 and 170 are denoted with
the same reference numerals. The components given the same
reference numerals are described in the first embodiment and thus
will not be described in this embodiment.
2.1 Shape of First Viscoelastic Body
FIG. 14 is a front perspective view showing an example of a
configuration of the rotary damper 170 of this embodiment. FIG. 15
is a front perspective view showing examples of configurations of
the first viscoelastic body 173, the contact member 77, and the
second viscoelastic body 74 of this embodiment. FIG. 16 is a front
perspective view describing an example of a shape of the first
viscoelastic body 173 of this embodiment.
Like the rotary damper 70 of the first embodiment, the rotary
damper 170 transmits the driving force from the motor 61 (see FIG.
2) to the photoreceptor drum 13. As shown in FIG. 14 and FIG. 15,
the rotary damper 170 mainly includes the first rotary member 71,
the second rotary member 72, the first and the second viscoelastic
bodies 173 and 74, the guide member 76, and the contact member
77.
Like the first viscoelastic body 73 of the first embodiment, the
first viscoelastic body 173 is disposed in the insertion hole 71a
of the first rotary member 71. As shown in FIG. 16, the first
viscoelastic body 173 has a trapezoidal shape as viewed in a
direction parallel with the rotation direction (indicated by the
arrow AR1).
Thus, as shown in FIG. 16, a width W1 on the farther side (e.g.,
load position LP1) of the first viscoelastic body 173 is set to be
smaller than a width W2 on the rotational shaft 70a side (for
example, load position LP2) of the first viscoelastic body 173.
Specifically, as shown in FIG. 16, the first viscoelastic body 173
has the uniform thickness Th from the rotational shaft 70a side to
the farther side, and has the width W gradually decreasing toward
the farther side from the rotational shaft 70a side.
The spring constant K of the first viscoelastic body 173 at each of
the load positions LP1 and LP2 can be regarded as being equal to
that obtained by arranging a plurality of spring bodies having the
same thickness Th in parallel. Thus, assuming that the first
viscoelastic body 173 at each of the load positions LP1 and LP2
includes two spring bodies (respectively having spring constants k3
and k4), the spring constant K of the first viscoelastic body 173
at each of the load positions LP1 and LP2 can be expressed as in
the following formula (2). K=k3+k4 (2)
FIG. 17 is a graph showing a relationship between the spring
constant K of the first viscoelastic body 173 at a position to
which the load is applied and the width W of the first viscoelastic
body 173 at the position. In FIG. 17, the horizontal axis
represents the width W (mm) of the first viscoelastic body 173, and
the vertical axis represents the spring constant K (N/m) of the
first viscoelastic body 173 corresponding to the width W. Leader
lines of the reference numerals LP1 and LP2 in FIG. 17 indicate
respectively the widths W and the spring constants K at the load
positions LP1 and LP2 of the first viscoelastic body 173.
As can be understood from the formula (2) and FIG. 17, the spring
constant K at each of the load positions LP1 and LP2 in FIG. 17
increases as the width W of the first viscoelastic body 173
increases.
Thus, the spring constant K of the first viscoelastic body 173 on
the farther side is smaller than the spring constant K of the first
viscoelastic body 173 on the rotational shaft 70a side. If a
constant torque is transmitted between the first and the second
rotary members 71 and 72, the compressive load received by the
first viscoelastic body 173 from the contact member 77 gradually
decreases toward the farther side from the rotational shaft 70a
side.
Thus, even when the contact member 77 moves toward the farther side
of the rotational shaft 70a in accordance with the aging of the
second viscoelastic body 74 due to use, the torsion angles of the
first and the second rotary members 71 and 72 are kept within a
predetermined range.
2.2 Advantage of Rotary Damper of Second Embodiment
As described above, as in the first embodiment, in the rotary
damper 170 of the second embodiment, the contact member 77 moves
toward the farther side from the rotational shaft 70a side along
the first viscoelastic body 173 in accordance with the aging of the
first viscoelastic body 173. Thus, a predetermined vibration
damping effect can be stably obtained.
The width W1 of the first viscoelastic body 173 on the farther side
is set to be smaller than the width W2 of the first viscoelastic
body 173 on the rotational shaft 70a side. Thus, the spring
constant K of the first viscoelastic body 173 on the farther side
is smaller than the spring constant K of the first viscoelastic
body 173 on the rotational shaft 70a side. If the constant torque
is transmitted between the first and the second rotary members 71
and 72, the compressive load applied to the first viscoelastic body
173 from the contact member 77 gradually decreases toward the
farther side from the rotational shaft 70a side.
Thus, even when the contact member 77 moves to the farther side in
accordance with the aging of the second viscoelastic body 74 due to
use, the torsion angles of the first and the second rotary members
71 and 72 can be kept within a predetermined range.
3. Third Embodiment
Next, a third embodiment of the present invention will be
described. The configuration of the third embodiment is the same as
that of the first embodiment, except that, in a rotary damper 270
of the third embodiment, the first and the second viscoelastic
bodies 73 and 74 of the first embodiment are replaced with
viscoelastic bodies having different material property. In the
third embodiment, the position of the first viscoelastic body 73 to
which the compressive load is applied moves toward the radial
direction side of the rotational shaft 70a in accordance with the
change in the used environment of the rotary damper 270 due to the
change in a surrounding temperature. Thus, the differences are
mainly described below.
FIG. 18 is a graph showing an example of a relationship between an
elastic coefficient E of the first and the second viscoelastic
bodies 73 and 74, and a temperature T in this embodiment. In FIG.
18, the vertical axis represents the elastic coefficient E (kPa)
and the horizontal axis represents the temperature T (.degree. C.).
Elastic coefficient-temperature curves C1 and C2 in FIG. 18
respectively correspond to the first and the second viscoelastic
bodies 73 and 74.
As can be understood from the curves C1 and C2 in FIG. 18, the
elastic coefficient E of each of the first and the second
viscoelastic bodies 73 and 74 respectively corresponding to the
curves C1 and C2 tends to decrease along with the increase in the
temperature T. Thus, the spring constant of the viscoelastic body
decreases along with the temperature rise.
Accordingly, when the viscoelastic bodies described in FIG. 18 are
used as the first and the second viscoelastic bodies 73 and 74, the
elastic coefficient of each of the first and the second
viscoelastic bodies 73 and 74 changes in accordance with the
temperature, and the rotary damper 270 operates as follows.
Specifically, if the elastic coefficient and the spring constant of
the second viscoelastic body 74 decrease along with the temperature
rise, the length of the second viscoelastic body 74 in the movement
line 76c gradually decreases along with the temperature rise (see
FIG. 11 and FIG. 13). Accordingly, the position where the first
viscoelastic body 73 receives the compressive load from the contact
member 77 gradually moves toward the farther side from the
rotational shaft 70a side along the first viscoelastic body 73 (see
FIG. 10 and FIG. 12).
If the constant torque is transmitted between the first and the
second rotary members 71 and 72, the compressive load received by
the first viscoelastic body 73 from the contact member 77 decreases
toward the farther side from the rotational shaft 70a side.
As described above, the temperature rise reduces the compressive
load applied to the first viscoelastic body 73 and the spring
constant of the first viscoelastic body 73. Thus, the first
viscoelastic body 73 can receive the compressive load at a position
corresponding to the temperature. Therefore, the torsion angles of
the first and the second rotary members 71 and 72 are kept within
the predetermined range and the predetermined vibration damping
effect can be stably obtained.
Since the position where the compressive load is received changes
in accordance with the temperature, the compressive load is not
always applied to the same position. Thus, the reduction of the
vibration damping effect due to the aging of the first viscoelastic
body 73 can be prevented. Specifically, the position can move
toward the farther side in accordance with the temperature rise,
and can return to the rotational shaft 70a side in accordance with
the temperature drop. Thus, aging of the first viscoelastic body 73
is reduced compared with a case where the compressive load is
always applied to a position on the rotational shaft 70a side.
By adjusting the thickness Th (see FIG. 7) and the width W (see
FIG. 16) of the first viscoelastic body 73 as in the first
embodiment, the torsion angles of the first and the second rotary
members 71 and 72 can be more surely kept within the predetermined
range, and the predetermined vibration damping effect can be more
stably obtained.
4. Fourth Embodiment
Next, a fourth embodiment of the present invention will be
described. The configuration of the fourth embodiment is the same
as that of the third embodiment, except that in a rotary damper 370
of the fourth embodiment, the second viscoelastic body 74 that
contracts in accordance with the change in the used environment
caused by the temperature change around the rotary damper 270 of
the third embodiment is replaced with an extension member 374.
Thus, the difference is mainly described below.
4.1 Configuration of Rotary Damper
FIG. 19 and FIG. 20 are respectively front and rear perspective
views showing an example of a configuration of the rotary damper
370 of this embodiment. Like the rotary damper 270 of the third
embodiment, the rotary damper 370 transmits the driving force from
the motor 61 (see FIG. 2) to the photoreceptor drum 13. As shown in
FIG. 19 and FIG. 20, the rotary damper 370 mainly includes the
first and the second rotary members 71 and 72, the first
viscoelastic body 73, the guide member 76, the contact member 77,
and the extension member 374.
The extension member 374 is made of a material that deforms in
accordance with a temperature such as bimetal and shape memory
array. As shown in FIG. 20, the extension member 374 is disposed in
a guide hole 72a of the second rotary member 72. Thus, the length
of the extension member 374 along the movement line 76c (see, for
example, FIG. 4) changes in accordance with the temperature.
As shown in FIG. 20, the block 76a and the second viscoelastic body
74 are inserted in the guide hole 72a with the extension member 374
and the block 76a being respectively disposed on the rotational
shaft 70a side and the farther side. Thus, when the temperature of
the space in which the rotary damper 370 is disposed rises and thus
the extension member 374 extends along the guide hole 72a, the
extension member 374 moves the block 76a towards the farther side
from the rotational shaft 70a side.
If the constant torque is transmitted between the first and the
second rotary members 71 and 72, the compressive load received by
the first viscoelastic body 73 from the contact member 77 decreases
toward the farther side from the rotational shaft 70a side.
As described above, when the extension member 374 extends along the
guide hole 72a due to the temperature rise, the compressive load
applied to the first viscoelastic body 73 decreases. The
temperature rise also reduces the spring constant of the first
viscoelastic body 73. Thus, the first viscoelastic body 73 can
receive the compressive load at a position corresponding to the
temperature. Thus, the torsion angles of the first and the second
rotary members 71 and 72 are kept within a predetermined range, and
a predetermined vibration damping effect can be stably
obtained.
Accordingly, the effect that is the same as that of the third
embodiment can be obtained. The thickness Th and/or the width W of
the first viscoelastic body 73 is set in such a manner that when
the contact member 77 is at any position corresponding to the
temperature, the vibration damping effect can be kept at a
predetermined level. For example, the thickness Th and/or the width
W of the first viscoelastic body 73 is set in such a manner that
the spring constant becomes lower at a position more on the farther
side.
5. Modification
The present invention is not limited to the embodiments described
above, and can be modified in various ways.
(1) It is described in the first and the second embodiments that
the elastic coefficient of each of the viscoelastic bodies 73, 74,
and 173 decreases in accordance with passage of time due to use.
However, the configuration is not limited to this. For example, a
configuration may be employed in which the elastic coefficient
increases in accordance with the aging due to use.
(2) It is described that the elastic coefficients of the first and
the second viscoelastic bodies 73 and 74 of the third embodiment
decrease along with the temperature rise. However, the
configuration is not limited to this. For example, the first and
the second viscoelastic bodies 73 and 74 having elastic coefficient
increasing along with the temperature rise may be employed. Here,
the contact position at which the contact member 77 contacts the
first viscoelastic body 73 moves towards the rotational shaft 70a
side from the farther side along with the temperature rise.
(3) It is described that the extension member 374 of the fourth
embodiment extends along with the temperature rise. However, the
configuration is not limited to this. For example, the extension
member 374 that contracts along with the temperature rise may be
employed. In this case, the block 76a and the second viscoelastic
body 74 are inserted in the guide hole 72a with the extension
member 374 and the block 76a being respectively disposed on the
farther side and the rotational shaft 70a side of the guide hole
72a.
In first to ninth aspects of the present invention, a contact
position of a contact member to a first viscoelastic body is
movable. Thus, when the torque is transmitted between first and
second rotators, a predetermined vibration damping effect can be
stably obtained.
Particularly, in the second aspect of the present invention, the
contact position of the contact member to the first viscoelastic
body is movable in the radial direction of the rotational shaft in
accordance with passage of time. Thus, the first viscoelastic body
can transmit the torque at a position free of aging due to use.
Therefore, a predetermined vibration damping effect can be stably
obtained.
Particularly, in the third aspect of the present invention, the
contact position of the contact member to the first viscoelastic
body is movable in the radial direction of the rotational shaft in
accordance with a change in a surrounding temperature. Thus, the
first viscoelastic body can receive the compressive load at a
position corresponding to the temperature. Accordingly, torsion
angles of the first and the second rotators are kept within a
predetermined range, and thus a predetermined vibration damping
effect can be stably obtained.
Particularly, in the fifth aspect of the present invention, when
the torque is transmitted between the first and the second
rotators, the length of an elastic member changes. For example, the
length of the elastic member increases in accordance with
temperature rise, and thus the position of the first viscoelastic
body where the compressive load is received gradually moves toward
the farther side of the rotational shaft from the rotational shaft
along the first viscoelastic body.
Thus, by associating the temperature change of the first
viscoelastic body and the length of the elastic member
corresponding to the temperature, the torsion angles of the first
and the second rotators are kept within the predetermined range,
and thus a predetermined vibration damping effect can be stably
obtained.
Particularly, in the sixth aspect of the present invention, when
the torque is transmitted between the first and the second
rotators, a resultant force of a reaction force produced by being
in contact with the first viscoelastic body and a centrifugal force
produced by rotation causes the compressive deformation of a second
viscoelastic body.
For example, the length of the second viscoelastic body along a
movement line gradually decreases in accordance with aging due to
use, and thus the position of the first viscoelastic body where the
compressive load is received from the contact member gradually
moves toward the farther side of the rotational shaft from the
rotational shaft side along the first viscoelastic body.
For example, if the elastic coefficient of the second viscoelastic
body decreases along with the temperature rise, the length of the
second viscoelastic body along the movement line gradually
decreases along with the temperature rise. Thus, the position of
the first viscoelastic body where the compressive load is received
from the contact member gradually moves toward the farther side of
the rotational shaft from the rotational shaft side along the first
viscoelastic body.
Thus, by associating the aging of the first viscoelastic body and
the aging of the second viscoelastic body for example, the first
viscoelastic body can transmit the torque between the first and the
second rotators at a position free of the aging due to use.
Therefore, a predetermined vibration damping effect can be stably
obtained.
Furthermore, by associating the temperature change of the first
viscoelastic body and the temperature change of the second
viscoelastic body for example, the torsion angles of the first and
the second rotators are kept within the predetermined range, and
thus the predetermined vibration damping effect can be stably
obtained.
Particularly, in the seventh aspect of the present invention, the
thickness of the first viscoelastic body on a farther side is set
to be larger than the thickness of the first viscoelastic body on a
side of the rotational shaft. Thus, the spring constant of the
first viscoelastic body on the farther side is smaller than the
spring constant of the first viscoelastic body on the rotational
shaft side. If a constant torque is transmitted between the first
and the second rotators, the compressive load received by the first
viscoelastic body from the contact member gradually decreases
toward the farther side of the rotational shaft from the rotational
shaft side. Thus, even when the contact member moves toward the
farther side from the rotational shaft, the torsion angles of the
first and the second rotators can be kept within the predetermined
range.
Particularly, in the eighth aspect of the present invention, the
width of the first viscoelastic body on the farther side is set to
be smaller than the width of the first viscoelastic body on the
rotational shaft side. Thus, the spring constant of the first
viscoelastic body on the farther side is smaller than the spring
constant of the first viscoelastic body on the rotational shaft
side. If a constant torque is transmitted between the first and the
second rotators, the compressive load received by the first
viscoelastic body from the contact member gradually decreases
toward the farther side of the rotational shaft from the rotational
shaft side. Thus, even when the contact member moves toward the
farther side from the rotational shaft, the torsion angles of the
first and the second rotators can be kept within the predetermined
range.
In the ninth aspect of the present invention, the rotary damper
according to any one of the first to the eighth aspects is
provided. Thus, even when the running torque of a developing roller
and an image carrier changes, a predetermined vibration damping
effect can be stably obtained.
For example, the vibration produced by the change in the running
torque of the developing roller due to increase/decrease of the
developer can be prevented. Thus, poor imaging due to the vibration
of the developing roller can be prevented. For example, in a
configuration where the image carrier and the developing roller
receive the torque from the same driving source, transmission of
the vibration to the image carrier due to the change in the running
torque of the developing roller can be effectively prevented. Thus,
poor imaging due to the vibration of the image carrier can be
prevented.
Obviously, numerous modifications and variations of the present
invention are possible in light of the above teachings. It is
therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
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